Most of usual security devices attached to the window or the door of a building are ordinarily attached afterward to the lock part of the window or the door. These security devices are easily externally detected and the operations thereof can be intentionally stopped by breaking glass or the door.
Further, in such usual security devices, the wiring of a power source for operation needs to be attached afterward. When the usual security devices are attached to all the windows or the doors of one house, a facility cost or a construction cost is extremely increased. In addition thereto, power always needs to be supplied to all the security devices. Thus, a running cost is undesirably increased.
Still further, in the usual security device, a plurality of the same kinds of devices needs to be attached, so that a specific opening or closing position is hardly instantaneously decided. Further, since the usual security device functions as a single member, the usual security device is hardly combined with other security system. Accordingly, the usual security device has great many problems to be solved in practice.
The above-described problems are common to those of a monitor device for monitoring the entrance to or exit from the building or the room, or a device for monitoring a parking or leaving state in a parking place.
As means for solving the above-described problems, a method may be considered by which each of the above-described states can be monitored under a non-power source state by making use of a piezoelectric power generating device using a piezoelectric ceramics element.
A piezoelectric material has various application aspects as a converting element between mechanical energy and electrical energy. As materials showing a piezoelectric effect, many materials of both inorganic materials and organic materials are well-known. As materials that are currently put to practical use, materials such as a PZT type ceramics (piezoelectric ceramics) are exemplified.
The piezoelectric ceramics element is an element provided with piezoelectric characteristics formed in such a way that high D.C voltage is applied to a polycrystalline material to generate remanence. Since a basic piezoelectric constant can be relatively freely changed depending on the composition of the piezoelectric ceramics element, a use thereof is wide. Especially, the piezoelectric ceramic element composed of lead zirconate titanate (PZT) has a wide selection range of composition ratio or additives and a variety of application ranges.
The usual piezoelectric power generating device using the piezoelectric ceramics element is formed by uniting a piezoelectric ceramics element plate to a base made of an acrylic material and fixing both the end parts of the base by holders made of a hard material such as metal. Then, steel balls are dropped on the ceramics element plate to apply mechanical impact energy due to a collision to the piezoelectric element plate, excite a flexural oscillation on the piezoelectric element plate including the base and take out electric energy.
However, although the practicability of the usual PZT type piezoelectric ceramics element is anticipated, a quantity of generated energy is very small. Thus, the usual PZT type piezoelectric ceramics element is undesirably deficient in its practicability. This problem arises, because the piezoelectric power generating device using the piezoelectric ceramics element of this type has important factors, for instance, the natural oscillation of the piezoelectric ceramics plate essentially needs to be continued as long as possible and how a strong and effective impact force is applied to the piezoelectric ceramics element.
However, most of the usual piezoelectric power generating devices do not have a support structure that the natural oscillation of the piezoelectric ceramics element plate does not accompany a mechanical resistance and a structure that the impact force to the piezoelectric ceramics element is still applied by steel balls as disclosed in, for instance, Japanese Patent Application Laid-Open No. 2001-145375. When an adequate quantity of generated energy is to be obtained in the structure using the steel balls, under these circumstances, there is no means other than a method that many steel balls are allowed to collide with the piezoelectric ceramics element as many as possible.
With the above-described circumstances taken into consideration, the present invention is devised. It is an object of the present invention to provide a non-power source type monitor device installed in a place where a non-power source system needs to be used or a place preferably suitable for the non-power source system, in which a quantity of generated energy not lower than several ten times as much as an output of electric current obtained by the usual piezoelectric power generating device using the steel balls can be assuredly obtained by striking a piezoelectric ceramics element once and a piezoelectric power generating device is formed commonly with means capable of automatically repeatedly striking the piezoelectric ceramics element so that a quantity of generated energy of a practical level can be assuredly ensured as a power source of such type of monitor device.